As we all know in Carhae a Roman army about 40.000 men strong was crushed by the Parthian horse archers and cataphracts.
Many historians believe that the main reason for that disastrous defeat was the bad leadership of Crassus (and the lack of support from the Roman senate, who did not sanctioned this campaign).
So what if instead Crassus was Caesar in command of the Roman troops?
Could this defeat avoided? Could it be a Roman victory? Or would Caesar simply not do it?

Please don't make ridiculous this topic. If you don't have anything to write then please don't.

That wasn't my intention, although the remark may have been flippant, it is nevertheless true. Changing commanders at Carrhae would have made litte difference to the course of the battle itself.

That said, with Caesar in command in those circumstances; when the battle was joined, I would have expected him to have extricated his army and prevented a complete disaster. Many people blame Crassus’ arrogance and inexperience, often forgetting that Marcus Antonius, a much more experienced general, got himself into a similar fix when he invaded Parthia, only he managed to save his army albeit with heavy casualties

From what we know of Caesar, I think he probably would have planned the campaign differently, by going via Armenia for example, using the Armenians as allies with a better knowledge of the area. Of course, the down side of this would have been that he would eventually be facing the entire Parthian army instead of just Surena’s command. Everything revolves around where the Parthian’s would be forced to give battle.

The Parthians had several weaknesses that an active, clever commander could have exploited. As the Romans fought the Parthians more, they got to learn their weaknesses and as often as not won subsequent encounters. The late Republican army however, was not really up to the job.

A) He was by no mean a better general than Crassus who had been the victor of Colline gate Gate and Silarus river

and

B) He made a worse mistake by starting out too late in the figthing season

Contrast this to Publius Ventidius who handed the Parthians three beatings and killed their three best commanders.

Between the defeats of Crassus and Antonius, even before Ventidius, there was Cassius Longinus, who defeated the Parthians with the remnants of Crassus' army. So I am not sure if I agree that the commander would have made no difference. What Longinus and Ventidius knew is that the Parthian knights, due to their Frahaang, or chivalry, were only too eager to fight. Ventidius used slingers, but the real success was just in presenting them with tough terrain for the cavalry to manuever. Longinus knew that the knights could be made victims of their own tactics of feighned retreat.

Final point- contrary to the myth of Carrhae in which arrows penetrated shields as if they were not there (thanks Plutarch), it was actually a two day battle in which the army initially retreated in good order. As literally hundreds of thousands of arrows were used, this simply could not have been the case if they were so effective against the Roman shields. I think Ceasar might have done a better job of retreating, or even holding his ground and provoking a fight with the knights.

As we all know in Carhae a Roman army about 40.000 men strong was crushed by the Parthian horse archers and cataphracts.
Many historians believe that the main reason for that disastrous defeat was the bad leadership of Crassus (and the lack of support from the Roman senate, who did not sanctioned this campaign).
So what if instead Crassus was Caesar in command of the Roman troops?
Could this defeat avoided? Could it be a Roman victory? Or would Caesar simply not do it?

Armies and terrain are the same as original.

Ancient military sources were subject to strong chauvinistic biases; in the (ostensibly atypical) Roman case their historians were so exceptionally harsh with the own seriously defeated commanders (let say MT Varro at Cannae) that contrary to other nations they tended to depict the debacles of such commanders as utterly embarassing personal blunders even in spite of exceptional numerical superiority (exceptional especially as opposed to the regular Roman victorious reports systematically against all odds).

The case of ML Crassus at Carrhae was paradigmatic and the deliberate unfavorable comparison with the divine CJ Caesar by lavish later Imperial historians couldn't have been more evident, especially regarding Appianus & LM Plutarchus, so their answer to the OP couldn't have been any more obvious.

A more objective assessment (let say by the historian Donald Earl within his The Era of Augustus) must reach different conclusions.

Just remember that ML Crassus Junior (son of then informal triumvir) the very right hand of his father at Carrhae, had actually been a rather distinguished legate of the Proconsul CJ Caesar during several campaigns at Gallia, especially for the conquest of Aquitania.

The Parthians would eventually become a regularly beatable Roman neighbor, but by the time of the Republican Civil Wars they proved to be too hard a nut to crack, and hardly just for ML Crassus; after long years of failed invasions from both sides Augustus would eventually formalize a stalemate between both empires.